Consider this hypothetical scenario. The Iranian parliament, the Majles, assembles and hardliners begin railing against the country’s chief nuclear negotiator, Mohammed Javad Zarif. They call for a vote of impeachment and the measure narrowly passes. Nuclear negotiations with the U.S. are thrown into chaos. Many Iranian MPs, clerics, and newspapers gleefully claim the talks no longer have legitimacy.

As evidence for the vote of impeachment, the hardliners’ Exhibit A is the letter sent to Iran’s leaders, drafted by Senator Tom Cotton, and signed by Senator Rand Paul.

After all, the conservatives reason, why should we place any more faith in Zarif? Didn’t America just admit the negotiations are a charade, to be canceled on a whim by the next president?

Could this happen? Fortunately it isn’t likely, but there is significant precedent. Last year, hardliners in the Majles tossed out Iran’s science minister, who they felt was doing too much to liberalize the country’s universities. They also barely lost a vote to censure Zarif, who stood accused of calling the Holocaust a “horrifying tragedy.” After Zarif was photographed in January taking a friendly stroll with John Kerry, hardliners summoned him back to the Majles for another round of haranguing.

This is the atmosphere in which Zarif is operating: one of strife between conservatives who view any rapprochement with America as a betrayal of the Islamic Revolution, and moderates who want to open up their country to the rest of the world. Zarif and President Hassan Rouhani are two of Iran’s most prevalent moderate faces, so hardliners are constantly snapping at their heels.

American policy, at the very least, should be to not do anything that will empower the hardliners and undermine the moderates. Yet that’s exactly what Cotton’s letter does. It’s another pound of leverage that Iran’s most intransigent traditionalists can bring to bear against Rouhani, Zarif, and the United States—and given Cotton’s desire to kill the Iran talks outright, that may have been its intent.

My friend Jim Antle argued on this blog yesterday that Paul’s signature on Cotton’s letter was substantively inconsequential and politically savvy. “The political reality is that whatever impact the letter has on the negotiations, it was going to have with 46 signatures,” Jim writes. He continues: “Consequently, there was no upside for Paul to deny Cotton a 47th signature and allow more hawkish rivals like Marco Rubio to continue to call him ‘the chief cheerleader of Obama’s foreign policy.'”

Jim is correct that the letter would have caused a splash even without Paul’s signature. But there are times when one has to cast aside political considerations and make decisions based on what’s best for the country. Ultimately, Paul being a signatory to that letter undermines the national interest—he’s only one forty-seventh of the problem, but part of it nevertheless.

And what if my nightmare scenario does come true? Paul will have to stand up at a GOP candidates debate and make the case for both an Iranian nuclear deal and his being party to a letter that helped squash an Iranian nuclear deal. Doing that without tripping over one’s shoelaces is an impossible task.

I’m no doe-eyed purist. I understand that politicians sometimes triangulate their positions to be more effective and agree with Jim that Paul is “doing more than any other single senator to slow the march to war.” Paul should absolutely talk tough against Iran and President Obama while working with Barbara Boxer to sharpen the teeth on a nuclear deal.

But even from the perspective of a coldhearted political realist, it’s hard to see what advantage Paul gains here. Nothing less than full-throated bloodlust against Iran will stop hawks from calling him a squish. Meanwhile he’s spooked his base of anti-war conservatives and fed the developing narrative that he’s a opportunist willing to mortgage his principles.

I appreciate the tricky position Paul is in. But in the case of Cotton’s sabotage mission, he went too far. Sometimes bad policy is also bad politics.